[urq] Why are the L5 Turbo engine sounds different ?

[John Cody Forbes]

>> in Quebec speaking French, someone born in Paris, and someone born in
>> Haiti, but if you ask me it sounds like they are just all speaking
>> French and thats that ;-).
> 
> 
> Right, and that's why we're asking Audifans, not cunning linguists,
> about Audis, not language accents. 

> <snip>
 
> Cheers,
> Brady


Well excuuuuse me for using what I thought to be a moderately entertaining analogy to help my point, which it seems you missed entirely. 

The bottom line here is that there are many differences in the 10v and 20v engines that change the acoustic properties. I could insert another analogy about different size and length tubing in a trumpet vs a coronet, but I guess that isn't acceptable. You have two distictly different cylinder heads with a different number of differently shaped exhaust ports that couple to differently shaped and sized exhaust headers. Different stuff makes different results. 

I would venture to say that the 'pulse' difference you hear has alot to do with the exhaust header. The 10v engines use basically two different header designs that I know of. The non-turbo engines use somewhat of a log style header where the cylinder 1 header primary tube runs rearward and the rest of the cylinders dump into that tube rather then having thier own primary tubes. The the turbo 10v headers are halfway between a proper header and a log - cylinder 1 gets it's own primary tube, but 3&4 and 2&5 share for at leas parts of thier path to the turbo. Both of these designs have no pulse tuning whatsoever which means that the pressure pulses of exhaust exiting the engine will not reach the turbo at evenly spaced intervals. Some pulses will be colliding and creating louder sounds, while other pulses might be landing in a void and being muffled a little. The 20v's that I'm familiar with have much much better header designs, especially the CQ bundle of snakes header, but also the AAN style are designed so that each cylinder gets it's own header primary that feeds into a collector. They aren't precisely equal nor tuned length, but they are significantly better.

-Cody Forbes